The invention relates to a bus communication architecture, more particularly for distributed and/or multi-computing systems.
Existing input/output busses, e.g. the PCI I/O bus, are basically designed to interconnect a processor board with input/output boards (“devices”), e.g. hard disk controllers. Bus bridges may be used in a number of cases: for example, a system-to-PCI bus bridge may be provided between a processor or system bus within a board and the PCI bus itself; a PCI-to-PCI bus bridge may be used where the number of existing devices is higher than the maximum connection capability of a single PCI bus; various other bus bridges may also be used where connection to another bus operating differently is desired, for example PCI to ISA, or PCI to SCSI.
Generally, a PCI I/O bus provides parallel processing for a plurality of boards, including I/O boards, and one or more processor boards. Where several processor boards are present, one of them may act as a master board.
Communication between the boards may be enabled by providing in each board a memory area which is made accessible from the bus, or, in other words, “exported” on the bus. A communication mechanism is also necessary. An example of such a mechanism has been proposed in: “Compact PCI, Multi-Computing Interface Specification”, PICMG 2.14 D0.60, May 12, 2000, PCI Industrial Computer Manufacturers Group (in short “PICMG”). Although interesting, the PICMG approach appears to be much hardware-dependent, and therefore raises certain problems, for example where use on a different bus architecture may be required.